1. Field of the Invention
The present invention relates to a speed controller with a pilot check valve for controlling the rate of flow of a fluid under pressure which is led from a fluid pressure device such as a cylinder, for example, and the rate of flow of a fluid under pressure which is supplied to the fluid pressure device.
2. Description of the Related Art
There have heretofore been used fluid pressure control circuits including a speed controller for controlling the rate of flow of a fluid under pressure that is discharged from and introduced into a fluid pressure device such as a cylinder, for example.
FIG. 7 of the accompanying drawings shows a conventional fluid pressure control circuit 1. As shown in FIG. 7, the fluid pressure control circuit 1 comprises a cylinder 2 having first and second fluid inlet/outlet ports 3, 6, a first speed controller 4 and a first pilot check valve 5 which are connected in series to the first fluid inlet/outlet port 3, a second speed controller 7 and a second pilot check valve 8 which are connected in series to the second fluid inlet/outlet port 6, and a solenoid-operated valve 9 connected to the first speed controller 4 and the second speed controller 7.
The fluid pressure control circuit 1 basically operates as follows: When the solenoid-operated valve 9 is shifted to one position, i.e., to the right in FIG. 7, a fluid, typically air, under pressure supplied from a pressure fluid source (not shown) flows through the first speed controller 4 and the first pilot check valve 5 into the first fluid inlet/outlet port 3, from which the fluid under pressure enters one of cylinder chambers of the cylinder 2. As the piston of the cylinder 2 moves toward the other cylinder chamber under the pressure of the supplied fluid, a fluid under pressure in the other cylinder chamber is discharged from the cylinder 2 and flows through the second pilot check valve 8 and the second speed controller 7 into the solenoid-operated valve 9, from which the fluid under pressure is discharged into the atmosphere. The speed of travel of the piston of the cylinder 2 can be controlled by adjusting the rate of flow of the fluid through the second speed controller 7 to a desired value.
The first speed controller 4 and the second speed controller 7 are made of identical components, but are separate from each other, and the first pilot check valve 5 and the second pilot check valve 8 are also made of identical components, but are separate from each other.
Therefore, the fluid pressure control circuit 1 is constructed of two speed controllers 4, 7, two pilot check valves 5, 8, and a single solenoid-operated valve 9. The solenoid-operated valve 9 is connected to the first and second speed controllers 4, 7 by conduits such as tubes. The second speed controllers 4, 7 are connected to the first and second pilot check valves 5, 8 by conduits such as tubes. The first and second pilot check valves 5, 8 are connected to the cylinder 2 by conduits such as tubes.
The fluid pressure control circuit 1 is made up of a large number of parts and hence expensive to manufacture because the two speed controllers 4, 7 and the two pilot check valves 5, 8, which are separate from each other, are combined with the cylinder 2. The space that is required to accommodate the pipes is relatively large and cannot be reduced.
The process of assembling the fluid pressure control circuit 1 is tedious and time-consuming because the two speed controllers 4, 7, the two pilot check valves 5, 8, and the solenoid-operated valve 9 need to be interconnected by the pipes.